The present invention relates to a pressure accumulator especially for hydraulic systems in control mechanisms of electric high-voltage lines, and more particularly to a tight closure of such pressure accumulator.
Pressure accumulator of this kind, usually consist of a cylinder whose end faces are each closed.
In a known pressure accumulator the end faces of the cylinder are closed by a lid which is to be inserted in the cylinder. The lid has one peripheral area which abuts the end face of the cylinder and is provided with a flange portion which is in engagement with a groove formed in the cylinder wall. The lid is further provided with a recess at its peripheral area which extends into the cylinder. In this recess, an annular seal is located which is of elastic material. In order to fasten the lid to the cylinder, a threaded ring is screwed with the end section of the cylinder. Within the interior of the cylinder, a plunger is located thereby dividing the interior into two sections which are respectively connected with a line system of a pressure medium and with a pressure cushion of compressed gas. The latter section is connected with a gas pressure generator.
In order to have a permanent and reliable operation of such pressure accumulator, the sealing of the end faces of the cylinder is of great importance. In the known pressure accumulator, the sealing ring is of O-shape and made as previously mentioned of elastic material e.g. synthetic caoutchouc. As will be described herein below, such O-shaped sealing rings do have considerable drawbacks. The sealing must resist fluctuations in temperatures of approximately from 40.degree. C. to +80.degree. C. and pressures up to 375 bar. Although there exist sealing materials which retain their functions within such a temperature range, however, they are not suitable for gaseous medium at pressures up to 375 bar. Under these circumstances, the gas diffuses through the material, especially upon very low temperatures. A further stress factor for the material resides in the fluctuations in pressure which can amount to up to 100 bar upon each switching step in the hydraulic system of the control mechanism. Such fluctuations in pressure may damage the material of the sealing rings in its structure, unless those sealing rings even with mirror deficiencies are separated during the manufacture of such pressure accumulators. Such a procedure is not only very cumbersome but also the production of sealing rings having such a high standard is hardly manageable by the concerned producers. Even, in case some producers are in a position to manufacture such high-quality sealing rings, the amount of rejected sealing rings is too high so that the expenses with respect to the material as well as to the necessary manual inspection are uneconomical.
Further, it is to be noted that upon using a lid composed of a cover plate and a cover member movable with respect to the cover plate, the cross section of the annular groove formed between these structural parts can be diminished against the resistance of the sealing ring. When using a sealing with the known O-shaped cross section, a relatively small contact surface is subjected to the total pressure acting actually on the sealing and this causes some diffuculties. Thus, the sealing ring will considerably be deformed thereby exposing the cylinder walls to a considerable radial pressure which could lead to a bulging out of the cylinder.